Thromboxane (TX) is a vasoactive hormone which is known to be involved in renal physiology and pathophysiology. To identify the site of action of TX in the kidney, we examined the distribution of this receptor in the normal rat kidney using a polyclonal antibody against TX receptor we had raised. Western immunoblot of rat kidney membrane fractions with the antibody identified a single protein band at the predicted molecular mass of rat TX receptor protein. In the rat kidney, immunostainable TX receptor was observed in glomeruli, arterial walls, luminal membranes of thick ascending limbs of Henle's loop, the luminal and basolateral membranes of either distal convoluted tubules or connecting tubules, and the basolateral membranes of collecting tubules. The localization of TX receptor provides better understanding of the mechanism of previously reported effects of TX on glomerular and tubular functions leading to hypertension as well as renal parenchymal diseases.